Which function cannot be performed by an R-S flip-flop?

An R-S flip-flop, also known as a reset-set flip-flop, is a basic digital memory circuit that can hold a state (either set or reset) depending on its input signals. Each of the options describes a different functionality associated with flip-flops.

The ability to hold a state is fundamental to the R-S flip-flop, allowing it to maintain its output based on past inputs. It is designed to store a single bit of information as well, which is another primary function of such flip-flops. When it comes to switching states, the R-S flip-flop can do this as its inputs change from one condition to another.

However, toggling in a strict sense usually implies that the flip-flop changes its output state (from 0 to 1 or 1 to 0) with certain signal conditions. In the case of constant R-S inputs, the R-S flip-flop will not toggle; instead, it will remain in whatever state it was set to. With one input high (set) and the other low (reset), the output will be determined by those fixed inputs rather than toggling. Therefore, the R-S flip-flop is not capable of toggling states when both inputs are held constant